mysql协议学习(三)--OK报文

Payload of OK Packet

Type	Name	Description
int<1>	header	[00] or [fe] the OK packet header
int<lenenc>	affected_rows	affected rows
int<lenenc>	last_insert_id	last insert-id
if capabilities & CLIENT_PROTOCOL_41 {
int<2>	status_flags	Status Flags
int<2>	warnings	number of warnings
} elseif capabilities & CLIENT_TRANSACTIONS {
int<2>	status_flags	Status Flags
}
if capabilities & CLIENT_SESSION_TRACK {
string<lenenc>	info	human readable status information
if status_flags & SERVER_SESSION_STATE_CHANGED {
string<lenenc>	session_state_changes	session state info
}
} else {
string<EOF>	info	human readable status information
}

对于执行成功的命令，通常会返回OK报文

OK报文和EOF报文的区别

对于OK报文和EOF报文，其header字段都可能为0xfe，那么有如下规则来区分这两种报文
OK Packet：length of packet > 7

EOF Packet：length of packet < 9

eg：

OK with CLIENT_PROTOCOL_41. 0 affected rows, last-insert-id was 0, AUTOCOMMIT enabled, 0
warnings. No further info.

07 00 00 0200000002 0000 00

...........

Status Flags说明：

Flag	Value	Comment
SERVER_STATUS_IN_TRANS	0x0001	a transaction is active
SERVER_STATUS_AUTOCOMMIT	0x0002	auto-commit is enabled
SERVER_MORE_RESULTS_EXISTS	0x0008
SERVER_STATUS_NO_GOOD_INDEX_USED	0x0010
SERVER_STATUS_NO_INDEX_USED	0x0020
SERVER_STATUS_CURSOR_EXISTS	0x0040	Used by Binary Protocol Resultset to signal that COM_STMT_FETCH must be used to fetch the row-data.
SERVER_STATUS_LAST_ROW_SENT	0x0080
SERVER_STATUS_DB_DROPPED	0x0100
SERVER_STATUS_NO_BACKSLASH_ESCAPES	0x0200
SERVER_STATUS_METADATA_CHANGED	0x0400
SERVER_QUERY_WAS_SLOW	0x0800
SERVER_PS_OUT_PARAMS	0x1000
SERVER_STATUS_IN_TRANS_READONLY	0x2000	in a read-only transaction
SERVER_SESSION_STATE_CHANGED	0x4000	connection state information has changed

Session State Information
该部分信息由以下部分组成：

Type	Name	Description
int<1>	type	type of data
string<lenenc>	data	data of the changed session info

其中type有3种，分别是：

types of State Change Information

Name	Value	Description
SESSION_TRACK_SYSTEM_VARIABLES	0x00	one or more system variables changed. See also: session_track_system_variables
SESSION_TRACK_SCHEMA	0x01	schema changed. See also: session_track_schema
SESSION_TRACK_STATE_CHANGE	0x02	"track state change" changed. See also: session_track_state_change

不同type类型对应的data组成是不同的

SESSION_TRACK_SYSTEM_VARIABLES 对应的data字段内容

Type	Name	Description
string<lenenc>	name	name of the changed system variable
string<lenenc>	value	value of the changed system variable

eg：
SET autocommit = OFF

00 0f 0a 61 75 74 6f 63 6f 6d 6d 69 7403 4f 46 46

....autocommit.OFF

第1个字节00表示type=SESSION_TRACK_SYSTEM_VARIABLES，接下来的部分组成为data字段，类型是string<lenenc>，其中第1个字节0f表示接下来的字符串长度为15个字节（0x0f = 15），而SESSION_TRACK_SYSTEM_VARIABLES的data字段又分为两个字段 name（string<lenenc>）和 value（string<lenenc>），那么接下来的 0a
61 75 74 6f 63 6f 6d 6d 69 74 （len = 0x0a） 和 03
4f 46 46 （len = 0x03）则分别为name字段和value字段的内容。

SESSION_TRACK_SCHEMA 对应的data字段内容

Type	Name	Description
string<lenenc>	name	name of the changed schema

eg：
USE test

01 05 04 74 65 73 74

...test

第1个字节01表示type=SESSION_TRACK_SCHEMA，接下来的部分组成为data字段，类型是string<lenenc>，其中第1个字节05表示接下来的字符串长度为5个字节，data字段内容为 04
74 65 73 74（len = 0x04）

SESSION_TRACK_STATE_CHANGE 对应的data字段内容

备注：A flag byte that indicates whether session state changes occurred. This flag is represented as an ASCII value

Type	Name	Description
string<lenenc>	is_tracked	[31] ("1") if state tracking got enabled.